The present invention relates to sensors for detecting vehicle impact, for the deployment of air bags or other responses to a vehicle collision. The invention further relates to impact detection systems and vehicles incorporating same. In particular, the invention relates to a deformation sensor installed within the crush zone of a vehicle, which operates by sensing changes in intensity of light or other waveform energy, within a carrier medium, wherein the local intensity of the lighting increases in the event of deformation of the medium.
Impact detection devices comprise an important element of the safety system of modern vehicles. The advent of air bags and automatic belt tighteners in particular have given rise to a need for accurate and responsive impact detection means. Desirably, detection means for vehicle use are relatively inexpensive. Further, it is essential that the sensors be highly reliable, and not be adversely affected by corrosion, temperature changes, altitude, etc.
Collision or impact sensors conventionally employ an accelerometer located in vehicle mid-body of the passenger compartment to detect rapid changes in vehicle velocity. However, these arrangements do not provide adequate information in respect of the location and severity of a collision event. The design and activation or increasingly sophisticated occupant restraint systems such as multiple air bags and seat belt tighteners render it important to sense the dynamics of an impact event in order to properly control the restraint devices. A greater degree of sensitivity and accuracy may be achieved through the use of crush zone sensors, which can be used to detect abrupt velocity changes within one or more of the impact zones of a vehicle. The crush zones are the regions within the vehicle which experience substantial deformation in the event of an impact, and which typically experiences a greater deceleration than the non-crush zone. The latter zone typically houses the passenger compartment. The crush zones typically comprise the trunk and engine compartments and the exterior regions of the door and side panels.
Conventional vehicle impact sensors include xe2x80x9cball-in-tubexe2x80x9d sensors and xe2x80x9cinertiaxe2x80x9d sensors. The ball-in-tube type sensor consists of a hermetically sealed housing, which encloses and surrounds a cylinder. A sensing ball-shaped piston is disposed within the cylinder, and the housing is filled with a damping gas. The piston includes electrically conductive elements. The piston resists movement within the cylinder, conventionally by means of a spring. When the device experiments a sufficient velocity change, the force experienced by the piston overcomes the countervailing bias exerted by the spring and displaces the piston within the cylinder. In addition to the force of the spring, the piston is also exposed to a damping force exerted by ambient damping gas, resulting from the pressure differential that exists once the piston has moved a specific distance within the cylinder. If the vehicle deceleration is sufficiently large in magnitude and long enough in duration to overcome both the damping force and the spring-biasing force, the piston will move to a position where contact is made with a circuit that will activate the air bag or other safety system.
An inertia type sensor operates on a similar principle, and comprises a moveable element, which is moveable relative to a static element. In one conventional version, an inertia sensor comprises a xe2x80x9crollamaticxe2x80x9d type sensor, which comprises a nearly frictionless mechanism consisting of two or more rollers inserted within the loops of a flexible band, with the band acting to turn the rollers whose movement can be directed to perform various functions. The moveable element is held in place by the tension of the band and a surrounding housing. In the event of a collision or other sudden deceleration or acceleration, the resulting force displaces the moveable element. If the force is great enough in duration and magnitude, the moveable element will move a predetermined distance to a pin, which will be hit or dislodged, activating the air bag or other safety system.
Various other sensors have been proposed for use within crush zones, including simple electrical switches, electronic pressure switches, and rod and tube sensors. Conventionally, these sensors have been positioned at the outermost extremities of the crush zone. Other deformation centers have been described, particularly for lateral impact situations. These sensors detect either deformation extent of deformation velocity or, in some cases, a combination of both but with very limited resolution. In one aspect, sensors detect the extent of crushing of the vehicle itself as an indicator of the crash severity or velocity change. Such sensors conventionally initiate safety systems if the crush zone deforms to the extent that it makes contact with the sensor, which has been appropriately positioned within the vehicle. Typically, multiple deformation sensors are mounted at various locations within the vehicle.
Deformation sensors mounted within the vehicle crush zone conventionally operate by mounting a switch within the crush zone which when the vehicle experiences a sufficient impact, forces two elements of the switch together to create an electrical contact. For example, a fiber optic type switch may be mounted within the contact zone (See U.S. Pat. No. 4,988,862). Alternatively, two spaced apart conductors separated by an elastic member may be mounted within the crush zone, with the conductors contacting each other upon experiencing a sufficient impact. (See U.S. Pat. No. 4,995,639).
A further type of collision sensor is disclosed in Germany laid open application DE 4407763 A1 (Robert Bosch GmbH). This arrangement comprises a collision deformation sensor for mounting within the crush zone of a vehicle comprising first and second spaced apart substrates, each of which may be mounted to or comprise a corresponding vehicle component within the crush zone. Between the substrates, means are provided for detecting convergence of the substrates and to generate an electronic signal in response to the detected convergence. Means are also provided which are responsive to the electronic signal, for actuating an occupant restraint system. The detection means relies on a light guide, which becomes deformed when the substrates converge. Deformation of the light guide caused by crushing of the vehicle releases a portion of the light traveling through the guide out the side walls thereby attenuating the light intensity reaching the light detector.
None of these conventional arrangements are entirely suitable for detecting velocity changes within the crush zone of a vehicle in a manner suitable for sensing all or most potentially injurious accidents. In particular, inertial sensors have been found to trigger air bag restraint systems on short duration acceleration pulses, but not on longer duration pulses. As well, the ball-in-tube type sensor has had little success when responding to vertical and lateral acceleration, and only responds relatively well to longitudinal deceleration. Further, the ball-in-tube sensor may be adversely affected by temperature, with extremes of temperature adversely effecting the viscosity of the damping gas within the sealed housing.
A drawback within many prior art sensors resides in the risk of accidental triggering in response to a non-destructive or non-injurious impact. It is desirable to provide a deformation sensor which is integral to the primary structure of the vehicle and will with a high reliability not respond to any event other than an actual deformation of the structural and/or energy absorbing members of the vehicle. It is further desirable to provide a sensor that is highly reliable in adverse environments and relatively inexpensive to mass produce.
A drawback within many prior art sensors resides in the risk of accidental triggering in response to a non-destructive or non-injurious impact. It is desirable to provide a deformation sensor which is integral to the primary structure of the vehicle and will with a high reliability not respond to any event other than an actual deformation of the structural and/or energy absorbing members of the vehicle. It is further desirable to provide a sensor that is highly reliable in adverse environments and relatively inexpensive to mass produce.
Superior impact detection to address the above goals may be achieved through the use of a sensor which operates according to light or other wave energy scattering principles, rather than strictly electrical and/or mechanical means.
Within applicant""s previous PCT International application no. PCT/CA98/00686 there is disclosed a pressure sensor of general application, referred to herein as an xe2x80x9cintegrating cavityxe2x80x9d pressure sensor. This sensor which operates according to the principle whereby the intensity of light or other wave energy dispersed and scattering within an integrating cavity is increased as the region within which the energy is dispersed is diminished. According to this principle, a pressure sensor may comprise a compressible carrier medium of light or other wave energy, containing scattering centers for disbursing the light within the carrier medium. Wave energy source receiving means are associated with the carrier medium to transmit and receive, respectively, the wave energy to and from the carrier medium.
The term xe2x80x9clightxe2x80x9d will for convenience be generally used herein in reference to wave energy of any suitable type. It will be understood that other forms of wave energy including electromagnetic radiation in the non-visible spectra and sound may comprise the wave energy for use in the present invention.
The carrier medium of the integrating cavity-type sensor may be enclosed within a flexible envelope or a compressible housing or the like. Pressure applied to the envelope or housing compresses the carrier medium, thereby increasing the intensity of the light within the region surrounding the light source, in proportion to the decrease in volume of the carrier medium. The change in light intensity is detected by the receiver, which transmits the information to a signal processing means. The carrier medium is transparent or translucent to the particular light or wave frequency, and preferably includes multiple light scattering centers evenly disbursed throughout the medium. For example the medium may comprise a translucent foam material. Alternatively, the integrating cavity comprises a hollow chamber, the interior face of the chamber walls having light reflective and dispersive properties which fully diffuse any light entering the chamber to provide the light dispersion function. The enclosure comprises or forms an integrating optical cavity, which is defined as a region or volume either bounded by an enclosure and/or comprising a deformable material with the characteristic whereby illumination within the cavity undergoes multiple scattering reflections or refractions to thereby become effectively randomized and smoothed out in its distribution throughout the cavity. In such the cavity, at the limit, information about the original direction of illumination is eventually lost. An integrating optical cavity may be an air or gas filled enclosure, or may be a volume within a translucent solid such as a cellular matrix that provides optical scattering centers.
It is a characteristic of such a cavity that, for a light source with a constant power output, the light intensity within the cavity is a function of the volume of the cavity, the position of the light source and either the reflectance of the walls of the envelope or the density of scattering centers within the carrier medium. A reduction in the volume of the cavity causes a corresponding increase in the light intensity within the cavity. The cavity may be formed with virtually any shape, although certain extreme shapes may not respond ideally.
A pressure sensor of this type may take several convenient forms that are suitable for the purposes of the present invention. For example, the sensor may comprise an elongate, flattened member featuring multiple light sources and receivers. Alternatively, the scattering medium may comprise a block of foam shaped to fit within a defined cavity or receiving space.
The present invention relates to detection of vehicle impacts which are categorized as xe2x80x9cseverexe2x80x9d. This refers to impacts in which serious injury or death to one or more vehicle occupants is reasonably likely.
It is an object of the invention to provide a vehicle component comprising a sensing or detector means for detection of a vehicle impact, whereby the risk of accidental triggering is minimized. It is a further object to provide an impact sensor specifically adapted to detect actual deformation of the crush zone of a vehicle or other components of the vehicle, indicative of severe impact. to provide such detection by sensing means that minimize electrical and moving elements and components.
In accordance with the objects recited above, the present invention is a sensor for detecting deformation of a vehicle crush zone, of the general type comprising spaced apart substrates, which may comprise vehicle components with a means between the substrates to detect convergence and trigger an appropriate response such as an airbag or seatbelt tensioners. The invention is for detecting vehicle impacts rated as severe. In one aspect, the invention comprises:
a) a compressible carrier medium of wave energy transmitting material such as a polymeric foram having wave energy scattering centers disbursed therein;
b) a wave energy source in communication with the carrier medium, to provide a scattered energy volume within the medium containing fully scattered wave energy;
c) a wave energy receiver for detecting the integrated intensity of the fully scattered wave energy; and
d) signal coupling means to operatively connect the receiver with signal processing means for triggering an occupant restraint system when the receiver detects a change in said integrated intensity indicating a converging of the substrates, and a consequent compression of the carrier medium, at or above an extent indicative of a severe impact of said vehicle.
Preferably, the wave energy comprises light, and the carrier medium comprises a translucent foam material.
In a further aspect, the energy source and receiver comprise a fiber optic light source, associated with a fiber optic receiver in close proximity thereto. In a further aspect, multiple paired fiber optic light sources and receivers are provided within a fiber optic array.
Alternatively, the light source may comprise one or more LED units in proximity to the carrier medium, and the receivers may comprise photoreceptors. The LED""s and photoreceptors may be mounted to a circuit board in contact with the carrier medium.
In a further aspect, the invention comprises a vehicle bumper, having a rigid bumper support comprising the first substrate member, a bumper skin spaced apart from the support and comprising the second substrate member, whereby a hollow region is defined between the bumper skin and support. The hollow region is at least partly filled with an energy absorbing material comprising the carrier medium, which conveniently comprises translucent foam. At least one light source and receiver communicate with the carrier medium. Preferably, the light source and receiver are in close proximity to, in contact with, or embedded within the foam. Conveniently the source and receiver comprise a linear array of fiber optic or LED light sources and receivers mounted to the bumper support. In one version, fiber optic transmitters and receivers are individually associated with a control module, which comprises a light source communicating with the fiber optic cables. The module further comprises signal coupling means for receiving transmitted light from the fiber optic receivers and signal processing means for converting the intensity of the received light into a signal indicative of deformation of the carrier medium in the region surrounding the energy sources and receivers. Alternatively, the module communicates with a circuit board supporting an array of LED""s and photoreceptors in contact with the carrier medium.
In a further aspect, the invention comprises a vehicle panel, such as a door panel or other structural element, comprising a rigid frame element and a skin spaced apart therefrom, with the hollow region between the skin and frame element being at least partly filled with the deformable carrier medium, which preferably comprises a translucent foam material. One or more light sources and receivers as described above are mounted within the panel in contact with or communicating with the carrier medium, and preferably mounted to the frame element. A control module as described above is associated with the energy sources and receivers.
In a further aspect, the invention comprises a vehicle frame element, comprising a hollow vehicle structural member at least partly and preferably completely filled with said carrier medium, which preferably comprises a translucent foam material. A light source and receiver means, as characterized above, communicates with the carrier medium and is associated with a processor module as characterized above.
In a further aspect, the invention comprises a deformation sensor for installation within a vehicle, for detecting compressive forces between two relatively closely spaced vehicle components. In this aspect, the invention comprises a pair of spaced apart parallel plates, with the region between the plates filled with the carrier medium, preferably comprising translucent foam. Each plate is associated with a corresponding vehicle component whereby any convergence of the vehicle components, such as would occur in a collision for example, compresses the interstitial foam between the plates. Preferably, the lateral edges of the hollow region are bounded by constraining members for fully enclosing the space between the plates and retaining the foam fully between the outer plates. One or more light sources and receivers as described above are positioned within the carrier medium or otherwise coupled to or communicating with the carrier medium. The receiver or receivers are linked to a processor module.
In a further aspect, the invention comprises a longitudinal deformation sensor, for detection of relative displacement of comparatively widely separated vehicle components. In this aspect, the invention comprises an elongate hollow cylinder, the bore of which is partly filled with the carrier medium. One end of the cylinder is sealed. The carrier medium is retained within the cylinder by a slidable cylinder plunger disposed within the hollow bore of the cylinder and in contact with the carrier medium. One or more light sources and receivers as described above is positioned within the cylinder in contact with or communicating with the carrier medium, and preferably mounted adjacent the base of the cylinder. The cylinder body and bore are each mounted to respective vehicle components. Displacement of the associated vehicle components towards each other displaces the plunger within the cylinder, thereby compressing the carrier medium and signaling an impact event. A processor module associated with the energy sources and receivers may be positioned either within the interior of the cylinder or externally thereof.
In a further aspect, the invention comprises a vehicle, having an air bag or other impact response means, and one or more deformation sensors as described above mounted within the vehicle and operatively connected to the response means.
In a further aspect, the invention comprises a method for detection of a severe impact against a vehicle, of the type comprising the steps of providing a vehicle having incorporated therein a deformation sensor within a crush zone of the vehicle and communicating between the sensor and an occupant restraint system when said sensor detects a severe impact. The invention is characterized by the steps of:
a) providing a deformation sensor of the general type described above, comprising a compressible carrier medium, a light emitter and receiver, signal coupling means and signal processing means; providing such a sensor within the vehicle linking two vehicle components within the crush zone of the vehicle;
b) transmitting light from a source to a deformable carrier medium within said sensor to form an optical cavity defined by a region with said medium within which light from said source is fully scattered;
c) detecting the intensity of fully scattered and integrated light within said optical cavity and transmitting a resulting signal to signal processing means;
d) converting within said signal processing means said integrated light intensity level into an output electrical signal;
e) actuating an occupant restraint system upon detection of a change in said integrated light intensity within said optical cavity indicative of crushing together of said vehicle components indicative of a severe impact experienced by said vehicle.